Engine won't run tried pretty much everything

[Linnix17]

66cc brand less engine. I am a mechanic and I've checked just about everything

Engine turns over but will not fire at all not even one pop or miss fire.

Engine has compression.

Has fantastic thick bright spark.

I have tried different magneto. Different CDI different carburetor different types of gasoline and mixes. Many different spark plugs

With engine dry and fuel off empty carb. I have exhaust completely off. I can get the engine spinning and turn fuel on and choke and watch it go from air to mist coming out the exhaust port. Still not even one fire.

The key way and magnet are at 1 o'clock at tdc so timing seems perfect

Completely stumped here. Going to tear engine apart. Backward piston? Any ideas are appreciated. Thanks and hello guys. I appreciate it

 

[crassius]

these are dead-simple motors, so problem will be too - big air leak at carb, idle screw set way too far in, throttle cable holding slide up, clutch slipping just enough to keep starting revs down

what value did you get for compression?

 

[Linnix17]

I havnt tested it on a compression tester but I have had tones of these engines. It has plenty compression. Atleast enough to fire.

I have switched a fully working carb from my other engine bikes. So the problem is not carb.

Gasket on intake is solid and so is the manifold.

There is plenty vacuum pulling thru the carb

Thanks for helping me!

 

[crassius]

with a seal blown, piston will still compress whatever is already in cylinder, but a gauge will only read about 25lb in that case

 

[Linnix17]

I have had the engine completely dry and poured fuel into the spark plug hole and it still didn't even fire once

Could the timing be off so perfectly that it is sparking when the Chamber is dry?

 

[Linnix17]

But I had fuel misting out the exhaust port after every stroke? It seems like it's getting and compression fuel air mixture

 

[crassius]

timing is controlled by CDI (unless the stator or rotor on mag is installed upside down) - I once had two bad CDIs right out of the box, but that is rare

 

[crassius]

how it seems and what it is can be different - why not check compression?

 

[Linnix17]

Hmmm I confirmed the key way was at 1oclock at top dead center. And it has perfect spark outside the cylinder. Strong spark. I also tried two working Cdis from my other bikes and a different magneto

 

[crassius]

did you get the stator in right side up?